A disk drive system includes one or more magnetic recording disks and control mechanisms for storing data within approximately circular tracks on the disk. A disk is composed of a substrate and one or more layers deposited on the substrate (e.g., aluminum). A trend in the design of disk drive systems is to increase the recording density of the magnetic recording disk used in the system. One method for increasing recording density is to pattern the surface of the disk with discrete tracks, referred to as discrete track recording (DTR). A DTR pattern may be formed by nano-imprint lithography (NIL) techniques, in which a pre-embossed forming tool (a.k.a., stamper, embosser, etc.), having an inverse pattern to be imprinted, is pressed into an embossable film (i.e., polymer) disposed above a disk substrate to form an initial pattern of compressed areas. This initial pattern ultimately forms a pattern of raised and recessed areas. After stamping the embossable film, an etching process may be used to transfer the pattern through the embossable film by removing the residual film in the compressed areas. After the imprint lithography process, another etching process may be used to form the pattern in a layer (e.g., substrate, nickel-phosphorous, soft magnetic layer, etc.) residing underneath the embossable film.
One prior DTR structure contains a pattern of concentric raised areas and recessed areas under a magnetic recording layer. The raised areas (also known as hills, lands, elevations, etc.) are used for storing data and the recessed areas (also known as troughs, valleys, grooves, etc.) provide inter-track isolation to reduce noise. The raised areas may have a width less than the width of the recording head such that portions of the head extend over the recessed areas during operation. The recessed areas have a depth relative to fly height of a recording head and raised areas. The recessed areas are sufficiently distanced from the head to inhibit storage of data by the head in the magnetic layer directly below the recessed areas. The raised areas are sufficiently close to the head to enable the writing of data in the magnetic layer directly on the raised areas. Therefore, when data are written to the recoding medium, the raised areas correspond to the data tracks. The recessed areas isolate the raised areas (e.g., the data tracks) from one another, resulting in data tracks that are defined both physically and magnetically.
A press may be used to imprint embossable films residing on one or both sides of a disk substrate. The press utilizes a die for each side of the disk to be imprinted. The die is coupled to a stamper that is pressed into the film to form the imprinted pattern in the film. A DTR disk may not be viable if the imprinting surface of the stamper is not concentrically aligned with the center of a disk substrate. This requirement may be particularly important when data tracks are generated on both sides of the disk because the data tracks on each side need to be in co-axial alignment with each other. As such, the imprinting of an embossable film above a disk substrate requires an alignment step, in which a centerline of the disk is aligned with a centerline of the imprinting surface, before the embossable film is actually imprinted.
Conventional presses utilize 2 and 4 post precision die sets to attain alignment of the top and bottom dies used to imprint films on each side of a disk. A 4-post die set is illustrated in FIG. 1. One problem with such post die sets is that the posts contain bushings or ball bearing sleeves (guides) that wear out or seals that leak lubricant over repeated use. Another problem with such die sets is that the multiple posts hinder access to the die space. Furthermore, current specialized press alignment methods typically require the use of an air bearing supported die that is adjusted to correct for alignment offset. In addition, such presses must be stopped, the die must then be unclamped, supporting air pressure applied, positional adjustments made, supporting air pressure removed, and the die be re-clamped in order to secure the alignment. As a result, the use of such presses results in high maintenance costs due to frequent mechanical wear and breakdown of components, inconsistent accuracy and reliability, and slower manufacturing cycle times.